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  1. Teleoperation enables complex robot platforms to perform tasks beyond the scope of the current state-of-the-art robot autonomy by imparting human intelligence and critical thinking to these operations. For seamless control of robot platforms, it is essential to facilitate optimal situational awareness of the workspace for the operator through active telepresence cameras. However, the control of these active telepresence cameras adds an additional degree of complexity to the task of teleoperation. In this paper we present our results from the user study that investigates: (1) how the teleoperator learns or adapts to performing the tasks via active cameras modeled after camera placements on the TRINA humanoid robot; (2) the perception-action coupling operators implement to control active telepresence cameras, and (3) the camera preferences for performing the tasks. These findings from the human motion analysis and post-study survey will help us determine desired design features for robot teleoperation interfaces and assistive autonomy. 
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    Free, publicly-accessible full text available September 30, 2024
  2. Free, publicly-accessible full text available August 1, 2024

    Recent high angular resolution ALMA observations have revealed numerous gaps in protoplanetary discs. A popular interpretation has been that planets open them. Most previous investigations of planet gap-opening have concentrated on viscous discs. Here, we carry out 2D (axisymmetric) global simulations of gap opening by a planet in a wind-launching non-ideal MHD disc with consistent thermochemistry. We find a strong concentration of poloidal magnetic flux in the planet-opened gap, where the gas dynamics are magnetically dominated. The magnetic field also drives a fast (nearly sonic) meridional gas circulation in the denser disc regions near the inner and outer edges of the gap, which may be observable through high-resolution molecular line observations. The gap is more ionized than its denser surrounding regions, with a better magnetic field–matter coupling. In particular, it has a much higher abundance of molecular ion HCO+, consistent with ALMA observations of the well-studied AS 209 protoplanetary disc that has prominent gaps and fast meridional motions reaching the local sound speed. Finally, we provide fitting formulae for the ambipolar and Ohmic diffusivities as a function of the disc local density, which can be used for future 3D simulations of planet gap-opening in non-ideal MHD discs where thermochemistry is too computationally expensive to evolve self-consistently with the magneto-hydrodynamics.

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  4. Abstract We present Atacama Large Millimeter/submillimeter Array Band 3 data toward five massive young stellar objects (MYSOs), and investigate relationships between unsaturated carbon-chain species and saturated complex organic molecules (COMs). An HC 5 N ( J = 35–34) line has been detected from three MYSOs, where nitrogen (N)-bearing COMs (CH 2 CHCN and CH 3 CH 2 CN) have been detected. The HC 5 N spatial distributions show compact features and match with a methanol (CH 3 OH) line with an upper-state energy around 300 K, which should trace hot cores. The hot regions are more extended around the MYSOs where N-bearing COMs and HC 5 N have been detected compared to two MYSOs without these molecular lines, while there are no clear differences in the bolometric luminosity and temperature. We run chemical simulations of hot-core models with a warm-up stage, and compare with the observational results. The observed abundances of HC 5 N and COMs show good agreements with the model at the hot-core stage with temperatures above 160 K. These results indicate that carbon-chain chemistry around the MYSOs cannot be reproduced by warm carbon-chain chemistry, and a new type of carbon-chain chemistry occurs in hot regions around MYSOs. 
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    Free, publicly-accessible full text available June 27, 2024
  5. Abstract Crescent-shaped structures in transition disks hold the key to studying the putative companions to the central stars. The dust dynamics, especially that of different grain sizes, is important to understanding the role of pressure bumps in planet formation. In this work, we present deep dust continuum observation with high resolution toward the Oph IRS 48 system. For the first time, we are able to significantly trace and detect emission along 95% of the ring crossing the crescent-shaped structure. The ring is highly eccentric with an eccentricity of 0.27. The flux density contrast between the peak of the flux and its counterpart along the ring is ∼270. In addition, we detect a compact emission toward the central star. If the emission is an inner circumstellar disk inside the cavity, it has a radius of at most a couple of astronomical units with a dust mass of 1.5 × 10 −8 M ⊙ , or 0.005 M ⊕ . We also discuss the implications of the potential eccentric orbit on the proper motion of the crescent, the putative secondary companion, and the asymmetry in velocity maps. 
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    Free, publicly-accessible full text available April 26, 2024
  6. Free, publicly-accessible full text available April 19, 2024
  7. Using sunlight to produce hydrogen gas via photocatalytic water splitting is highly desirable for green energy harvesting and sustainability. In this work, Mn 2+ doped 1-dimensional (1D) CdS nanorods (NRs) with Pt tips ( i.e. , 1D Mn:CdS-Pt NRs) were synthesized for photocatalytic water splitting to generate hydrogen gas. The incorporation of Mn 2+ dopants inside the 1D CdS NRs with a significantly longer lifetime (∼ms) than that of host excitons (∼ns) facilitates charge separation; the electron transfer to metal Pt tips leads to enhanced photocatalytic activity in water splitting redox reactions. The as-synthesized Mn 2+ doped CdS NR-based photocatalyst generated an order of magnitude greater yield of hydrogen gas compared to the undoped CdS NR-based photocatalyst. The enhanced charge transport from the long lifetime excited state of Mn 2+ dopants in light harvesting semiconductor nanomaterials presents a new opportunity to increase the overall photocatalytic performance. 
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    Free, publicly-accessible full text available March 28, 2024

    We compare the structure of synthetic dust polarization with synthetic molecular line emission from radiative transfer calculations using a three-dimensional, turbulent collapsing-cloud magnetohydrodynamics simulation. The histogram of relative orientation (HRO) technique and the projected Rayleigh statistic (PRS) are considered. In our trans-Alfvénic (more strongly magnetized) simulation, there is a transition to perpendicular alignment at densities above ∼4 × 103 cm−3. This transition is recovered in most of our synthetic observations of optically thin molecular tracers; however, for 12CO it does not occur and the PRS remains in parallel alignment across the whole observer space. We calculate the physical depth of the optical depth τ = 1 surface and find that for 12CO it is largely located in front of the cloud mid-plane, suggesting that 12CO is too optically thick and instead mainly probes low-volume density gas. In our super-Alfvénic simulation, the magnetic field becomes significantly more tangled, and all observed tracers tend towards no preference for perpendicular or parallel alignment. An observable difference in alignment between optically thin and optically thick tracers may indicate the presence of a dynamically important magnetic field, though there is some degeneracy with viewing angle. We convolve our data with a Gaussian beam and compare it with HRO results of the Vela C molecular cloud. We find good agreement between these results and our sub-Alfvénic simulations when viewed with the magnetic field in the plane of the sky (especially when sensitivity limitations are considered), though the observations are also consistent with an intermediately inclined magnetic field.

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  9. Ultra-low velocity zones (ULVZs) are thin anomalous patches on the boundary between the Earth's core and mantle, revealed by their effects on the seismic waves that propagate through them. Here we map a broad ULVZ near the Galápagos hotspot using shear-diffracted waves. Forward modelling assuming a cylindrical shape shows the patch is ~600 km wide, ~20 km high, and its shear velocities are ~25% reduced. The ULVZ is comparable to other broad ULVZs mapped on the core-mantle boundary near Hawaii, Iceland, and Samoa.  Strikingly, all four hotspots where the mantle plume appears rooted by these ‘mega-ULVZs’, show similar anomalous isotopic signatures in He, Ne, and W in their ocean island basalts. This correlation suggests mega-ULVZs might be primordial or caused by interaction with the core, and some material from ULVZs is entrained within the plume. For the Galápagos, the connection implies the plume is offset to the west towards the base of the mantle. 
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    Free, publicly-accessible full text available October 28, 2023
  10. Motion tracking interfaces are intuitive for free-form teleoperation tasks. However, efficient manipulation control can be difficult with such interfaces because of issues like the interference of unintended motions and the limited precision of human motion control. The limitation in control efficiency reduces the operator's performance and increases their workload and frustration during robot teleoperation. To improve the efficiency, we proposed separating controlled degrees of freedom (DoFs) and adjusting the motion scaling ratio of a motion tracking interface. The motion tracking of handheld controllers from a Virtual Reality system was used for the interface. We separated the translation and rotational control into: 1) two controllers held in the dominant and non-dominant hands and 2) hand pose tracking and trackpad inputs of a controller. We scaled the control mapping ratio based on 1) the environmental constraints and 2) the teleoperator's control speed. We further conducted a user study to investigate the effectiveness of the proposed methods in increasing efficiency. Our results show that the separation of position and orientation control into two controllers and the environment-based scaling methods perform better than their alternatives. 
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    Free, publicly-accessible full text available October 23, 2023